Field of the Invention
The present invention is broadly concerned with aqueous liquid compositions containing anionic polymer(s), boron compound(s), and boron compound dispersant(s) or solvent(s), having relatively high, heretofore unattainable contents of non-precipitating boron compound(s). More particularly, the invention is concerned with such compositions preferably having one or more polymers including relatively high fractions of dicarboxyl repeat units, boric acid, and polyol or alpha-hydroxy acid dispersants or solvents, which find particular utility in agricultural contexts.
Description of the Prior Art
For a number of years, Specialty Fertilizer Products, LLC of Leawood, Kans., has commercialized a series of aqueous dispersions of maleic-itaconic copolymers in partial salt form. These products include AVAIL® for use with granular and liquid fertilizers (respectively the partial sodium and ammonium salts), and NUTRISPHERE-N® for use with granular and liquid fertilizers (the partial calcium salt). For example, such products may be sprayed or otherwise applied to the surface of solid fertilizers, such as urea, ammonium salts, monoammonium phosphate (MAP), diammonium phosphate (DAP), and gypsum, or mixed with liquid fertilizers, such as UAN and ammonium polyphosphate.
These prior products have been shown to have a number of outstanding agricultural properties, including the ability to enhance the uptake of fertilizer nutrients (e.g., phosphates, nitrogen, potassium, and micronutrients), to act as adjuvants for pesticides such as glyphosate herbicides, and, when supplemented with an organic drying agent, to very quickly dry when applied to solid fertilizers, thereby facilitating production of final coated solid fertilizer products. Moreover, the preferred copolymers have been shown to have enhanced activity when fertilizer formulations containing both the calcium and sodium copolymer partial salts are employed (U.S. Patent Publication No. 2009-0217723). This technology is also described in U.S. Pat. Nos. 6,515,090, 7,655,597, 7,736,412, and 8,043,995, and related patents.
It is also known that boron compounds, and especially boric acid, can be added to the maleic-itaconic copolymers described above to obtain beneficial agricultural results when mixed with or applied to solid nitrogenous fertilizers, such as granular urea, and liquid fertilizers, such as UAN. Specifically, the presence of boron compounds provides enhanced performance, especially in the prevention of loss of nitrogen from such nitrogen-containing fertilizers. U.S. Pat. No. 8,025,709 teaches that boric acid at a level of from about 0.5-5% can be used to supplement the maleic-itaconic copolymers, particularly when used with bimodal polyvinyl alcohols.
However, it has been found that the use of boron compounds such as boric acid is limited in that these compounds are difficult to maintain in dispersion or solution with desirable polyanionic polymers. Hence, while the advantages of relatively high boron compound loadings with polyanionic polymers are well known, there has heretofore been no way to maintain these compounds in effective dispersion or solution, particularly during long-term storage or under adverse (especially cold) storage conditions.
Boric acid solubility has been enhanced by the use of alcohols, usually methanol, in certain compositions. However, alcohols present problems associated with handling, toxicity, and flammability, and furthermore do not increase boric acid solubility to desirable levels.
Accordingly, there is a need in the art for improved aqueous anionic polymer compositions containing boron compounds, such as boric acid, at high levels, and without the use of methanol, and which maintain the boron compounds in effective dispersion or solution over relatively long storage times and adverse storage conditions.